WO2006035009A1 - Determination of the amplified spontaneous emission in an optical fibre amplifier - Google Patents

Abstract

The invention relates to a method for the determination of an amplified spontaneous emission (ASE) in an optical single- or multi-stage fibre amplifier, in other words with one or any number of serially-arranged amplifier stages each comprising a pumped amplification fibre. The invention is based on the fact that the generated ASE power within a single amplifier stage with constant mean inversion or constant gain value is approximately independent of the input power, so long as large powers are not coupled into the amplifier stage. The above feature is suitable for a determination of an ASE power (= power of the amplified spontaneous emission ASE) of the individual amplifier stages, which must be estimated and subtracted from the measured total power for an exact determination of the signal power at the amplifier output. Corresponding aspects of the embodiment of the device are disclosed for both single-stage and multi-stage optical fibre amplifiers such that the method can be fully carried out.

Description

Determination of amplified spontaneous emission in an optical fiber amplifier

The invention relates to a method for determining the amplified spontaneous emission (ASE = Amplified Spontaneous Emission) in an optical fiber amplifier according to the preamble of claim 1 and an associated data carrier according to the preamble of claim 12 and then a single-stage and a multi-stage optical fiber amplifier according to the preambles of the claims 16, 17.

Modern erbium doped fiber amplifiers for very long range WDM systems typically have three gain stages with gain fibers separated by components such as variable attenuators and dispersion compensating fibers, and have combined gain and output power control.

To measure a sum signal power at the input and the output of the amplifier photodiodes are used as a rule, but the measurement signals may be distorted, since the signals noise is superimposed in the form of the amplified spontaneous emission ASE. Especially with small channel numbers of a WDM signal to be amplified (WDM = Wavelength Division Multiplex), the resulting relative error can be large, especially since modern receivers with improved error correction methods (such as EFEC = Enhanced Forward Error Correction) allow low signal-to-noise ratios ,

In order to be able to set the required signal output power, it is therefore necessary to correct the measurement signal by the superimposed amplified spontaneous emission ASE by estimating the amplified spontaneous emission ASE generated in the individual amplifier as accurately as possible. Known methods use the following approximation to calculate the ASE power (amplified spontaneous emission power ASE) generated in an EDFA (optical bandwidth C-band amplifier B _opt = 4.44 THz):

P ^ASE = hv-B _opt -nf-g = 0.57045 • 10 ^"3 • nf ■ g {MW}

where B _{out stands} for the optical bandwidth, v denotes the mean carrier frequency of the signals (typically: 193.40THz, 1550nm), the variable g represents the EDFA gain, and nf denotes the EDFA noise figure.

In general, the EDFA noise figure nf is tabulated for a few operating points of the EDFA input power and the EDFA gain in the 40-channel mode. An exact calculation of the generated ASE power is therefore not possible because:

a variation of the passive losses in the EDFA can cause significant changes,

disregard spectral form factors (e.g., the gain-gain filter used),

the EDFA noise figure when operating with few channels (1 ... 10) may deviate significantly from the tabulated values for the 40 channel operation, i. the noise figure depends not only on the input power and, in addition to the gain, on the current channel assignment.

In a three-stage optical fiber amplifier, characterization of the amplifier encounters accuracy limits relatively quickly, only as a function of total gain from input to output and as a function of input power, because with equal gain, the passive losses between the individual stages can vary widely, which has a strong impact on performance generated ASE performance. The object of the present invention is to specify a method with which the amplified spontaneous emission ASE generated in a single-stage to multi-stage fiber amplifier EDFA can be determined with high accuracy.

A solution of the problem is in terms of their method aspect by a method having the features of claim 1 and in terms of their device aspect by a data carrier with the features of claim 12 and by a single-stage and a multi-stage optical fiber amplifier with the features of claims 16, 17th

Advantageous developments of the invention are specified in the subclaims.

The inventive method for determining, i. for determining the power of amplified spontaneous emission ASE in an optical fiber amplifier, i. With an arbitrary number of serially connected amplifier stages (which have at least one pumped amplification fiber), based on a concept, if appropriate, an approximation which can be derived from a single-stage fiber amplifier. In fact, it can be shown that, with a constant mean inversion or constant gain of an amplifier stage, the amplified spontaneous emission produced in this amplifier stage is almost independent of the input power. This aspect is very well suited for determining an ASE power (= amplified spontaneous emission power ASE) of the individual amplifier stage.

For multistage amplifier stages in an optical fiber amplifier, all contributions (in terms of powers) of the individual amplifier stages can be calculated according to the previous concept for the first time. Further will be cooperating ASE contributions of one amplifier stage to another amplifier stage also determined.

At the output of the entire fiber amplifier, the total amplified spontaneous emission ASE is simply and quickly determined as a sum of ASE contributions generated in individual amplifier stages multiplied by the transmission functions of subsequent components.

Furthermore, it is shown that the determination of the individual terms of the summation can be carried out with the aid of a few parameters which serve as predefined values for the method. For example, for a three-stage fiber amplifier, starting with only 2 inversion values, only 6 parameters are needed to use a table (to provide the predefined values) to determine all 6 contributions to the ASE power directly in conjunction with an input power. This table can at the beginning of the commissioning of the optical fiber amplifier or directly after the completion of the amplifier card (with the integrated optical fiber amplifier) by means of a

Calibration are generated as well as regularly updated during operation (for example, to take into account aging effects). The term "table" is to be understood in the general sense that the predefined values could also be stored electronically on a chip card, for example, in a completely different form than a table. multiple inversions at one or more amplifier stage (s).

Several embodiments of the invention on the basis of a single-stage, a two-stage and a three-stage fiber amplifier will be explained in more detail below with regard to the method aspects and the device aspects. From this, a person skilled in the art will be able to deduce, such as a determination of the total amplified spontaneous emission for any multi-stage fiber amplifier according to the invention takes place.

The method may also be applied to an optical transmission system having at least one transmission fiber and at least one switched optical fiber amplifier.

It is assumed in the following that the spectral shape of the input spectrum of the optical fiber amplifier is known or at least an estimate is present. A regulation adjusts the powers of pump signals in such a way that certain boundary conditions for the powers of the signals to be amplified are maintained at the outputs of the individual amplifier stages. For example, with regard to non-linear effects, it makes sense to select the gain of a second amplifier stage such that the strongest channel level at the input of a dispersion-compensating fiber has a certain optimum power value.

If the profit profile of individual amplifier stages z. B. erbium-doped fiber amplifier EDFA has been characterized, the average inversion to be set can be determined for each amplifier stage. With these characteristics, the ASE power generated in the erbium-doped fiber amplifier EDFA can be determined at individual measuring points and thus the desired signal power can be determined with high accuracy.

An embodiment of the invention will also be explained in more detail below with reference to the drawing.

Showing:

1 shows an ASE power generated in an amplifier stage as a function of the input power for various gain values, 2 shows a single-stage optical fiber amplifier,

Fig. 3 shows a three-stage optical fiber amplifier.

In FIG. 1, six profiles of the ASE power P _ASE generated in a single amplifier stage of the amplified spontaneous emission ASE in a single-stage fiber amplifier at respective gain values G = 14, 16, 18, 20, 22, 24 dB as a function of the input power P _1N I in the

Fiber amplifier incoming optical signal shown. The gain of an amplifier stage with a gain fiber (e.g., erbium-doped fiber) depends solely on an average of the inversion χ of that amplifier stage, but not on its course. To a good approximation, this can also be assumed for the ASE power generated in the amplifier stage with a pump. For all points belonging to one of the six curves, the mean inversion of the erbium-doped fiber is kept constant. In a very wide range of signal input powers, the generated ASE is constant and only at very high power does the ASE performance decrease. Taking into account that ASE correction is important only for small signal input powers, the dependence of the noise power on the input power in determining the ASE can be neglected. Under certain circumstances, the slight dependence on the input power can still be considered.

From Figure 1 is now the first embodiment, the

Output power P ^ ^SE the amplified spontaneous emission ASE calculated at the output of the first amplifier stage Vl a single-stage fiber amplifier.

The method, is set a predetermined output power P _OüT l for a measured EingangsIeistung P _1N I and therefrom an average inversion χ of the amplifier stage Vl _t determined. Such a procedure can also be carried out by presetting a predetermined _{profit value} instead of the output power P _oατ l. Such specifications at the end of the amplifier stage are important, for example so that no too high or too low power levels occur at the output of the fiber amplifier.

In other words, according to FIG. 1, the output power P ^{SE of} the amplified spontaneous emission ASE is determined immediately after knowledge of:

- the input power and the mean inversion or

- the input power and the profit value or

- the input power and the output power.

For example, in the first amplifier stage Vl an ASE power P ^ ^SE at a noise power density S ^ ^SE (λ, χ,) are generated, which depends on the mean inversion χ, the first amplifier stage Vl. Their contribution to a total ASE power P _ASE 1 at the output of the first amplifier stage Vl is:

where the interval [A ₀ ^ ₁ ] denotes that wavelength range in which significant power components occur, and the first parameter τ _u (χ,) is a function of the first mean inversion χ.

If values of the first parameter τ _n (χ,) as a function of the mean inversion χ have been stored in a table, a first output power P ^{SE of} the amplified spontaneous emission ASE at the output of the first amplifier stage V 1 can be determined immediately. In the single-stage fiber amplifier, the total ASE power P _ASE 1 is exactly the contribution P ^ ^SE . Further, an optical two-stage fiber amplifier is considered. The ASE output at the first stage output is calculated as described above for the single stage case.

Now, the first amplifier stage V1 contributes to the ASE power at the output of the second amplifier stage V2. Overall, the ASE power at the output of the first stage is composed of two contributions P ₁ ^ and P ₂ ^ ^SE , which respectively take into account the ASE generated in the first stage and the ASE generated in the second stage.

The contribution of the first stage to the total ASE power at the amplifier output can be calculated as follows:

₁ P ^ = fST (λ, _Xl) ^ G (λ, _n χ) a, dλ = U ₁ T _{12 (Xl, To).}

where G _π ^SE (λ, Zn) the gain of the second amplifier stage V2 at a mean inversion χ _{n of} the second amplifier stage V2, a, the attenuation between the first and the second

Amplifier stage and the parameter τ ₁₂ (znZπ) denote a function of the two mean inversions ^, χ _n .

Finally, the second amplifier stage V2 contributes to the total ASE power at the output of the second stage in a manner similar to the first amplifier stage Vl at its output, so that:

, T₂₂[X₁) nur von der mittlerenwhere Sf _j ^SE {λ, Zu) is a power density at the input of the second amplifier stage V2 and the parameter τ ₂₂ (χ _π ) is a function of the mean inversion χ _{n of} the second amplifier stage V2. Since an amplifier is usually operated in its operating state with a fixed profit profile (eg flat profit curve, ie identical gain for all channels), the mean inversion of both stages corresponds to a predetermined value, so that the parameters χ, and χ _n linearly depend on each other , The matrix T ₁₂ [χ ,, χ ") can thus be reduced to a vector (dependence of only one variable). If the total gain of all optical amplifier stages V 1, V 2 is kept constant, all three parameters depend

, T ₂₂ [X ₁ ) only from the middle

Inversion χ, from.

The total power P _ASE 2 of the amplified spontaneous emission ASE at the output of the two-stage optical fiber amplifier is calculated by adding the two contributions P ₁₂ ^SE and F ₂₂ ^SE .

Furthermore, this calculation for determining the ASE power contributions for other multi-stage fiber amplifier, as in the following for a three-stage fiber amplifier Vl, V2, V3, take place.

Six contributions P ₁ ^, P ₁ ^, P _: f ^E , P ₂ ^A ₂ ^SE , P ₂ f ^E , P ₃ f ^{E must} be determined. The first three contributions P ^ASE , P ₁₂ ^SE , Pff ^E are those from the first amplifier stage V 1 to each amplifier stage V 1, V 2, V 3. The two further contributions V ₂₂ ^E , P ₂ ^ASE are those from the second amplifier stage V2 to the second and third amplifier stage V2, V3. The last contribution P ₃ ^ASE is that from the third amplifier stage V3 to the same third amplifier stage V3.

So there is the following relationship:

ASE output at the first stage output:

= P / ASE output at the second stage output:

_ pASE pASE

- ^r l2 ^{■ "r} 22

ASE output at the third stage output: pASE _ _p ASE pASE pASE ^r 3 - ^r l3 ^" + ^{■ r} 23 ^" + ^{■ r} 33

The contributions P ^ ^SE , P ₁ ^ and P ^ ^SE can be calculated as in the previous embodiment with two amplifier stages:

C ^E = fcr {λ, _χi ) dλ = T ₁₁ or ₇ )

ie as a function of the mean inversions χ,, χ "of the first and the second amplifier stage Vl, V2.

The contribution P ₁ ^ can be calculated as follows:

p ^ASE ₌ ^ sr {λ, _XI) Gtr {λ, _{X n-)} G ^ {λ, χ _{m) ai} a _π dλ

where G% ^E {λ, χ _m ). GT {λ, χ _ιn ) _denote the spectral gains of the second and third amplifier stages V2, V3 as a function of the corresponding mean inversion χ _in (the third amplifier stage V3). In this case, the attenuation of the second amplifier stage is denoted by a ". Because of or at one

Keeping constant the total gain of the optical three-stage fiber amplifier follows the equation:

Gf ^SE {Ä, _Xl ) -G ^ ^E {Ä, _Xll ) -Gff {Ä, _Xw ) = G ₀ = const

With which the contributions, a function of the mean inversion χ _{m of} the third amplifier stage V3, as a function one or both other middle inversions χ _t , χ _π can be determined. That is, for a three-stage optical fiber amplifier, only two instead of three inversion values are needed to obtain the six contributions of the total power of the amplified spontaneous emission ASE, as follows:

P ₁ ^ASE a _l a _π dλ = a _l a _π - G ₀ - _Tn (Z ₁ )

The two further contributions P ₂ f ^E , P ₃ ^ASE can be calculated as follows:

I

T Pj ₂ A ₃ SE f ^ ¹ r. ASE \ r < ^ASE (^. \ D _A λI

I

If the total gain of the three-stage fiber amplifier is kept constant at the value G ₀ , the two last contributions can also be calculated as a function of the two mean inversions,, χ _n such that

11 )

11)

Overall, to accurately determine a total power P _ASE 3 of the amplified spontaneous emission ASE in the three-stage

Fiber amplifiers V1, V2, V3 can therefore use six inverse of two of the amplifier stages V1, V2, V3 to _obtain six parameters τ _n (χ,), τ ₁₂ (χ,), T ₂₂ Gf /) ' ^τ ÄXi) ■ ^τ iλXnXn) • ^ (XnXn) (as a function of the two selected inversions) are tabulated by means of a suitable calibration.

In operation, depending on the input power at an amplifier stage, the total ASE power at the end of the optical fiber amplifier is determined by adding the corresponding contributions selected in the tables become. This method can be implemented by means of a Digital Signal Processing (DSP) for real-time determination of the total ASE performance.

On the basis of the previous three embodiments of a single-stage, two-stage and three-stage optical fiber amplifier is one skilled obvious further investigation by the total power of the ASE ^τ by generating appropriate tables of calibrated values, _j {Zi'X _m ^etc) f ^ur a N derive step-stage fiber amplifier (N> 3).

This method can also be applied to amplifier stages with intermediate transmission fibers. For this purpose, only additional attenuation factors than the known previous attenuation values a,, a _u occur. Therefore one can at any chosen place or at the end of the

Transmission system perform a complete and accurate determination of ASE performance easily and quickly.

To carry out the method according to the invention, a data carrier can be used with a program which can be loaded into a control module, wherein the control module carries out the previous method when the named program is executed. This aspect is very important because the whole process can be controlled by software, monitoring or measuring device component or its output signals of the optical amplifier.

The control module may comprise one or more local control units in at least one of the gain stages. This allows accurate determination of the ASE power directly on the optical fiber amplifier. In connection with a power control of the signals or the pump signals of an amplifier stage, a power adjustment can take place independently on the optical amplifier. The control module may be part of a network management, especially if overall monitoring of a network is desired.

The tabulated values are most conveniently stored in a DSP-based module (DSP = Digital Signal Processing) controlled by the control module. Such a module allows a quick and extensive access to the values of the table and its processing z. B. by further addition and multiplication.

In the following, the invention will be considered from a device viewpoint. Two embodiments are described in which a new single-stage and a new three-stage optical fiber amplifier are shown.

FIG. 2 shows the single-stage optical fiber amplifier with an amplifier stage Vl (Erbium-doped fiber EDF pumped with pump source PUMP), at which a first power _measuring means M _1N and at the output second power _measuring means M _OüT or by means of a predetermined _{gain control} G _M0NIT0R (eg an AGC = Automatic Gain Control) are assigned a determination arrangement of the mean inversion. The _gain control G _M0NIT0R controls in this example, the power of the pump source PUMP, so that a default in terms of gain or output power at the output of the amplifier stage and the optical fiber amplifier is guaranteed. Instead of the profit regulation can also the two

Power _{measuring means} M _1N , M _{OÜT be used} to adjust a given gain by controlling the pump source PUMP. The same applies if the _{gain control} G _M0NIT0R and the output-side power _{measuring means} M _OüT are used.

In this case, output signals of the first power- _{measuring means} M _1N and the detection arrangement (here the profit regulation G _M0NIT0R ) of the mean inversion to one

Table TAB, in which different calibrated values of power contributions P ^ ^{SE of} an amplified spontaneous

Emission ASE are stored. The contributions provide the direct ASE overall performance of the optical fiber amplifier. The values calibrated in the table are the parameters τ _n (χ,) mentioned in FIG. 1 as a function of the mean inversion χ,.

In principle, however, an optical fiber amplifier with several amplifier stages V 1, V 2, V 3,... Will deviate slightly from that with an amplifier stage if it should be suitable for carrying out the method according to the invention.

3, the three-stage optical fiber amplifier is taken at whose amplifier stages V1, V2, V3 (with three serially connected and pumped amplification fibers EDF1, EDF2, EDF3) a respective first power _{measuring means} M _IN1 , M _IN2 , M _IN3 at the input ... and by means of an amplifier stage output side second power _measuring means M _OüT1 , M _OüT2 , M _OüT3 , ". or by means of a predetermined _{gain control} G _M0NIT0Rli G _M0NIT0R2 , G _M0NIT0R3 , ... are associated with a determination _{arrangement of} the mean inversion of this amplifier stage.

As in FIG. 2, output _{signals of} each first power _{measuring means are} M _IN1 , M _IN2 , M _IN3, and

Bestimmung der ASE in mehrstufigen Faserverstärkern erforderlich ist. Wie bereits bei der Beschreibung des erfindungsgemässen Verfahrens erwähnt, werden aus den verschiedenen kalibrierten Werten (=Parameter T₁₁(^₇), T₁₂(^₇) , τ₂₂(χ,) , T₁₃(χ,), T₂₃(χ,,χ_n) , ^r ₃₃{X_I'X_Ii) ) ^un<3 den Dämpfungen der Elemente zwischen den Stufen die ASE-Gesamtleistungen an den Ausgängen der einzelnen Stufen berechnet . Davon sollten nur sechs Parameter die richtigen Leistungsbeiträge abliefern, jedoch müssen sie noch ggf. multipliziert (mit Dämpfungswerten a, , a„ und ggf. Konstantgewinnwerten G₀) und anschliessend addiert werden.Determination order (s) G _M0NIT0R1 G _M0NIT0R2 , G _M0NIT0R3 the mean inversion led to the table TAB. However, the table TAB has many more calibrated values than in FIG. 2, since a larger number of parameters τ _u (χ,), τ ₁₂ (χ,), T ₂₂ (χ,),

Determination of the ASE is required in multistage fiber amplifiers. As already mentioned in the description of the method according to the invention, from the various calibrated values (= parameters T ₁₁ ( _{7 7} ), T ₁₂ ( _{7 7} ), τ ₂₂ (χ,), T ₁₃ (χ,), T ₂₃ (FIG. χ ,, χ _n ), ^r ₃₃ {X _I 'X _I i)) ^{and <} 3 the attenuations of the elements between the Levels are calculated as the total ASE performance at the outputs of each stage. Of these, only six parameters should deliver the correct power contributions, but they must still be multiplied if necessary (with attenuation values a, a "and possibly constant gain values G ₀ ) and then added together.

Therefore, the table TAB is followed by a linear adder ADD _LIN , whose addition components for determining a total power P _{ASE of} the amplified spontaneous emission ASE occurring at the output of the optical amplifier by means of selected calibrated values of the table

TAB are formed. In particular, when the tabulated values have been calibrated without systemic factors a, "a", G ₀ , ...), the multiplier to the adder ADD is required because a new weighting must be made. The linear adder ADD _LIN can also be used to recalibrate the values, eg in case of an aging effect or if the configuration in the optical fiber amplifier changes.

Claims

claims A method for power amplification of spontaneous emission (ASE) in an optical fiber amplifier for a WDM signal having at least a first amplifier stage (Vl) in which a predetermined output power (P _oo l) is set for a measured input power (P _1N I) and a first mean inversion {χ,) of the amplifier stage (Vl) is determined therefrom, characterized in that a first output power (P _ASE 1. 1) is determined on the basis of predefined, preferably tabulated values which depend on the first average inversions (χ,) ) of the amplified spontaneous emission (ASE) at the output of the first amplifier stage (Vl) is determined. 2. The method according to claim 1, characterized in that at one of the first amplifier stage (Vl) serially connected second amplifier stage (V2) a second predetermined output power (P _0ÜT 2) is set at a known output line of the first amplifier stage (Vl), and possibly From this a second average inversion {χ ") of the second amplifier stage (V2) can be determined that, with constant gain over both amplifier stages (V1, V2) and based on three tabulated values, from the first mean inversion (χ,) or depend on the second mean inversion (χ "), a second output power (P _ÄSE 2) of the amplified spontaneous emission (ASE) at the output of the first amplifier stage (Vl) and the second amplifier stage (V2) is determined. 3. The method according to claim 1, characterized in that in one of the first amplifier stage (Vl) serially downstream second amplifier stage (V2), a second predetermined output power (P _0ÜT 2) is set at a known output line of the first amplifier stage (Vl) and from a second average inversion {χ ") of the second amplifier stage (Vl) is determined that based on tabulated values of one or both mean inversion (χ,, χ _n ) depend, a second one Output power (P _ÄSE 2) of the amplified spontaneous emission (ASE) at the output of the second amplifier stage (V2) is determined. 4. Method according to claims 2 or 3, characterized in that two tabulated values

, possibly _u )), to which the ASE powers (P ^ ^SE , P ₂ ^ ^SE ) are proportional to outputs of the first or second amplifier stage (Vl, V2), calibrated before determining the total power (P _ASE 2) and that another tabulated value (T ₁₂ [χ ,, possibly _u )), to which the ASE power (P ₁₂ ^SE ) at outputs of the second Amplifier stage (V2) is proportional, before the determination of the total power (P _ASE 2) is calibrated. 5. The method of claim 2 or 3, characterized in that at a second amplifier stage (V2) serially connected third amplifier stage (V3) a third predetermined output power (P _0ÜT 3) is set at a known output line of the second amplifier stage (V2) and, if necessary from which a third average inversion (χ _iπ ) of the third amplifier stage (V3) can be determined, that with constant gain over the three amplifier stage (V1, V2, V3) and based on six tabulated values of which four values of one of the mean inversion (χ,, Xn _• Xm) ^{un <} 3 on the other hand depend on two values of two of the mean inversions (χ _,, χ _u , χ _IU ), a third output power (P _ESE 3) of the amplify spontaneous emission (ASE) at the output of the third amplifier stage (V3) is determined. 6. The method of claim 2 or 3, characterized in that at one of the second amplifier stage (V2) serially connected third amplifier stage (V3), a third predetermined output power (P _OüT 3) with known Output line of the second amplifier stage (V2) is set and from a third average inversion (χ _in ) of the third amplifier stage (V3) is determined that based on six tabulated values, from one to all of the mean inversion (χ,, χ _n , χ _ιn ) middle Inversion {χ,, χ ", χ,"), a third output power (P _ASE 3) of the amplified spontaneous emission (ASE) at the output of the third amplifier stage (V3) is determined. 7. The method according to claims 5 or 6, characterized in that three tabulated values {τ _n (χ,), τ ₂₂ {χ,, optionallyχ "), ^τ ii {Xi, XmSSf-Xm))> ^to which the ASE powers (P ^ ^SE , P ^SE , P ₃ ^ ^SE ) are proportional to outputs of the individual amplifier stages, prior to the determination of the total power (P _ÄSE 3) are calibrated and that two more tabulated values (τAXnSSf-Xπ) '* n {XnSgf-XmXm)), to which in turn the ASE powers (P ₁₂ ^SE , P ^ ^SE ) at outputs of the second and third Amplifier stage (V2, V3) are proportional, before the Determining the total power (P _ASE 3) are calibrated and that a last tabulated value (T ₂₃ (χ ,, χ ", if necessary, χ,")), which is proportional to from the second amplifier stage (V2) to the third amplifier stage (V3 ) contribution (P ASE 23 to the total power (P _ASE 3) is calibrated before the determination of the total power (P _ASE 3). 8. The method according to any one of claims 5 to 7, characterized in that further power contributions (P _y ^ΛSE ) with i = 1, 2, 3, 4 ,, 5, ... and j = 4, 5, ... in an optical fiber amplifier with More than three amplifier stages are determined to determine the overall amplified spontaneous emission (ASE) power of the optical fiber amplifier and added to total power values at the outputs of the individual amplifier stages. 9. The method according to claim 8, characterized in that all power contributions _(P; ^ΛSE) using tabulated values (τ _k, (χ _{I, II} ggf.χ, χ, ...) ") are determined, which in a pre-calibrated table were saved. 10. The method according to claim 9, characterized in that proportionality factors between power contributions and tabulated values are determined by system properties such as attenuation values or total gain values. 11. The method according to any one of the preceding claims, characterized in that the tabulated values are recalibrated regularly, so that aging or widening effects of the optical fiber amplifier are taken into account. 12. Data carrier with a program that can be loaded into a control module, wherein the control module performs the method according to one of claims 1 to 11, when the named program is executed. 13. A data carrier according to claim 12, characterized in that the control module is a local control unit at one of the gain stages. 14. A data carrier according to claim 12, characterized in that that the control module is part of a network management. 15. A data carrier according to any one of claims 12 to 14, characterized in that the tabulated values are stored in or read from a DSP-based module, which is controlled by the control module. 16. Optical fiber amplifier with an amplifier stage (Vl), at which at the input a first power measuring means (M_IN) and by means of an output side second Power measuring means (M_OUT) or by means of a predetermined _{gain control} (G _M0NIT0R ) associated with a determination _{arrangement of} the mean inversion, characterized in that output signals of the first power measuring means (M_IN) and the determination arrangement of the mean inversion to a Table (TAB) are stored in which various calibrated values of power values (P _ÄSE 1 = P ^ ^SE ) of an amplified spontaneous emission (ASE). 17. Optical fiber amplifier with several amplifier stages (Vl, V2, V3, ...), to each of which at the input a first power _{measuring means} (M _IN1 , M _IN2 , M _IN3 , ...) and by means of a Amplifier stage output side second power _{measuring means} (M _OüT1 , M _OüT2 , M ₀₀₁₃ , ...) or by means of a predetermined _{gain control} (G _{M0NIT0R1 /} G _M0NIT0R2 , G _M0NIT0R3 , ...) associated with a determination _{arrangement of} the mean inversion of this amplifier stage, characterized in that output _{signals of} the first power _{measuring means} (M _IN1 , M _IN2 , M _IN3 ,...) and the mean inversion determining _arrangement are led to a table (TAB) in which different calibrated values of power amplifier-related power contributions ( P ₁ T _' P ₁ T _' PifS P ₂ T _* P ₂ T _* P ₃ T- •••) of a reinforced spontaneous emission (ASE) are stored, that the table (TAB) is followed by a linear adder (ADD _LIN ), whose addition components for determining a total power (P _ÄSE ) of the amplified spontaneous emission (ASE) occurring at the output of the optical amplifier by selected calibrated Values of the table (TAB) are formed. The optical fiber amplifier according to claim 17, characterized in that the linear adder (ADD _LIN ) comprises a multiplier which weights each addition component from the table (TAB) with system-related factors such as attenuation values or constant gain values.